Method for producing metal carbonate and catalyst for producing the same

ABSTRACT

A method for producing metal carbonate is disclosed. The method includes the following steps of providing a first mixture of metal and a catalyst containing iron, NO groups, and N-containing ligands first; then introducing carbon dioxide to the first mixture to form a second mixture and obtaining a product. The method described here can improve the yield and decrease the cost of metal carbonate production.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefits of the Taiwan Patent ApplicationSer. No. 105103196, filed on Feb. 1, 2016, the subject matter of whichis incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for producing carbonate, moreparticularly, to a method for producing metal carbonate.

2. Description of Related Art

Metal carbonate is an important material for industry and is widely usedin medical and industrial fields. For example, zinc carbonates are usedas nutrient or medicine for zinc-deficient diseases or as astringent forcosmetics. Zinc carbonates are also major components of fire-resistantcompositions or absorbents for hydrogen sulfide used in petroleumcracking. Iron carbonates may also be used as absorbents for hydrogensulfide or as additives for animal feeds.

It is known that zinc carbonates can be produced through many processes.Currently, many zinc carbonates are synthesized through the followingknown synthetic route (which can be seen in the description of U.S. Pat.No. 1,944,415):

3ZnO+2CH₃COOH+CO₂+H₂→ZnCO₃·Zn(OH)₂·ZnO+2CH₃COOH

As illustrated by the above equation, the product zinc carbonates mixedwith Zn(OH)₂ and ZnO can be obtained. However, the known processes forproducing zinc carbonate or metal carbonate are complicated andenergy-consuming. In addition, further product separation orpurification is often required for high-purity applications.

Therefore, it is desirable to provide an improved method for producingmetal carbonate to mitigate and/or obviate the aforementioned problems.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a simple method forproducing metal carbonate with less energy consumption and improvedyield.

Another object of the present invention is to provide a simple methodfor producing metal carbonate at room temperature.

Another object of the present invention is to provide a compound forimproving the process for producing metal carbonate.

To achieve the object, the method for producing metal carbonate of thepresent invention includes the following steps: (A) providing a firstmixture of metal and a solution of a catalyst represented by thefollowing formula (I):

(Fe(NO)₂)₂L  (I)

wherein L is a ligand represented by the following formula (II);

(R₁R₂)N—(CH₂)₂—N(R₃)—(CH₂)₂—N(R₄)—(CH₂)₂—N(R₅R₆)  (II)

wherein each of R₁, R₂, R₃, R₄, R₅, and R₆ is hydrogen, or C₁-C₃ alkylindependently; and (B) introducing carbon dioxide to the first mixtureto form a second mixture and obtaining a product.

The compound of the present invention is represented by the followingformula (I):

(Fe(NO)₂)₂L  (I)

wherein L is a ligand represented by the following formula (II);

(R₁R₂)N—(CH₂)₂—N(R₃)—(CH₂)₂—N(R₄)—(CH₂)₂—N(R₅R₆)  (II)

wherein each of R₁, R₂, R₃, R₄, R₅, and R₆ is hydrogen, or C₁-C₃ alkyl,independently.

R₁ and R₂ of L of the present invention can be the same or different.Preferably, R₁ and R₂ of L are the same. R₃ and R₄ of L of the presentinvention can be the same or different. Preferably, R₃ and R₄ of L arethe same. R₅ and R₆ of L of the present invention can be the same ordifferent. Preferably, R₅ and R₆ are the same. Each of R_(i), R₂, R₃,R₄, R₅, and R₆ of L the present invention, as illustrated above, ishydrogen, or C₁-C₃ alkyl, independently. Preferably, R₁, R₂, R₃, R₄, R₅,and R₆ of L are hydrogen, or methyl. More preferably, L is1,1,4,7,10,10-hexamethyltriethylenetetramine, or triethylenetetramine.The metal carbonate of the present invention is not limited. Preferably,the metal of the metal carbonate of the present invention is Na, Mg, Zn,Fe, or the combination thereof. The compound of the present inventioncan be used as a catalyst for reactions. Preferably, the compound of thepresent invention is used as a catalyst for the reaction for producingmetal carbonate. More preferably, the compound of the present inventionis used as a catalyst for the reaction for producing sodium carbonate,magnesium carbonate, zinc carbonate, iron carbonate, or the combinationthereof.

The method of the present invention can optionally further include step(C) drying or filtering the second mixture to collect the product ofstep (B). The temperature for performing the method of the presentinvention is not limited. Preferably, the method of the presentinvention is performed at a temperature under 250° C. More preferably,the method of the present invention is performed at room temperature.The solution of the method of the present invention in step (A) is notlimited. Preferably, the solution is an organic solution or an aqueoussolution.

The method of the present invention can be completed using the compoundrepresented by formula (I). The general reaction of the method of thepresent invention can be described by the following reaction formula(III):

wherein M is metal.

Through the assistance of the compound of the present inventiondescribed above, metal carbonates can be synthesized in a simple waywith less energy consumption and improved yield.

Other objects, advantages, and novel features of the present inventionwill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The figure is an IR spectrum of [(HMTETA)(Fe(NO)₂)₂] Complex of Example1-1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Example 1-1 Synthesisof [(HMTETA)(Fe(NO)₂)₂] Complex (HMTETA: 1,1,4,7,10,10-Hexamethyltriethylenetetramine)

Compounds [Na][NO₂] (10.0 mmol, 0.690 g) and 18-crown-6-ether (10.0mmol, 2.643 g) were dissolved in THF in the 50 mL Schlenk flask, and thecommercial [Fe(CO)₅] (10.0 mmol, 1.348 mL) was added into the THFmixture solution at 0° C. The resulting solution was stirred at ambienttemperature overnight. The reaction was monitored with FTIR. IR spectrum(IR 1983 m, 1877 s (υ_(CO)), 1647 m (υ_(NO))) cm⁻¹ (THF)) was assignedto the formation of [Na-18-crown-6-ether][Fe(CO)₃(NO)]. Hexane was addedto precipitate the yellow solid [Na-18-crown-6-ether][Fe(CO)₃(NO)](3.885 g, 85%).

[18-crown-6-ether-Na][Fe(CO₃)NO] (1.828 g, 3 mmol) and [NO][BF₄](nitrosonium tetrafluoroborate) (0.467 g, 3 mmol) in a 50 mL Schlenkflask were weighted. THF (˜20 mL) was then added. After reacting duringmixing at room temperature for approximately 20 mins, Fe(CO)₂(NO)₂ (IR:2088s, 2037s, (ν_(CO)), 1808s, 1760s (ν_(NO)) cm⁻¹ (THF)) was produced.1,1,4,7,10, 10-Hexamethyltriethylenetetramine (HMTETA) (0.408 mL, 1.5mmol) was then added to the reaction solution using a plastic syringe.After reacting during mixing for 30 mins, IR vibrational frequency ofthe reaction solution was measured at 1693s, 1634s cm⁻¹ (ν_(No)) (THF).[(HMTETA)(Fe(NO)₂)₂] was speculated to have formed. Hexane was thenadded to the upper layer (volume ratio of hexane:THF was approximately4:1). Dark brown crystals were obtained after the reaction solution wasleft to stand for approximately 3 days. The structure of the dark browncrystals obtained was then identified using x-ray single crystaldiffraction analysis and IR (ν_(No)): 1693s, 1634 cm⁻¹ (THF) (shown inFIG. 1).

Example 1-2

Synthesis of [(TETA)(Fe(NO)₂)₂] Complex (TETA: triethylenetetramine)

THF solution of Fe(CO)₂(NO)₂ (prepared from the reaction of[18-crown-6-ether-Na][Fe(CO)₃(NO)] (1.828 g, 3 mmol) and [NO][BF₄](0.467 g, 3 mmol) in THF (20 mL)) and triethylenetetramine (TETA) (0.223mL, 1.5 mmol) was stirred at ambient temperature for 30 minutes. IRν_(NO) frequencies of 1688, 1630 cm⁻¹ indicate the formation of[(TETA)(Fe(NO)₂)₂]. Then addition of hexane into the reaction solutionled to dark-brown semi-solid [(TETA)(Fe(NO)₂)₂] (details described inExperimental Section). IR v_(NO): 1688, 1630 cm⁻¹ (THF).

Example 2

Synthesis of Carbonate Complex

Sodium metal strip (0.069 g, 3 mmol) in a 100 mL Schlenk flask wasweighted. The reaction flask was next put in a glovebox filled withnitrogen gas. Iron metal complex [(HMTETA)(Fe(NO)₂)₂] (0.0138 g, 0.03mmol) was weighted in the glovebox. THF (˜20 mL) was then added followedby supplying carbon dioxide gas (˜73.5 mL, 3 mmol) into the glovebox.After reacting during mixing for approximately 3 days in a sealedenvironment with no ventilation, white colored sodium carbonate (Na₂CO₃)was produced in the reaction flask. Gas at the headspace was analyzedusing gas chromatography 3 days later. A peak of carbon monoxide wasdetected (reaction formula 1). THF was then removed, water was added,and the solution was filtered and left to stand for several days. Untilwater had evaporated naturally, sodium carbonate (Na₂CO₃) crystals(0.144 g, 90% yield) were obtained. The structure of the sodiumcarbonate (Na₂CO₃) crystals was then identified using x-ray singlecrystal diffraction analysis.

Example 3-1 to 3-4

Zinc metal powder (0.6538 g, 10 mmol) in a 500 mL glass reaction flaskwas weighted in air. The reaction flask was next put in a gloveboxfilled with nitrogen gas. [(HMTETA)(Fe(NO)₂)₂] complex (0.046 g, 0.1mmol) was weighted and loaded into the flask in the glovebox. Aqueoussolvent (˜100 mL) was then added. Carbon dioxide gas (490 mL, 20 mmol)was bubbled into the reaction aqueous solution at room temperature andpressure. After reacting during mixing at room temperature and pressurefor 15 hrs, pure white colored zinc carbonate (ZnCO₃) was produced inthe reaction flask. The calculated yield was 1.125 g (89.7%) (Table 1,Entry 1). Gas at the headspace was analyzed using gas chromatography. Apeak of carbon monoxide was detected.

Next, zinc carbonates (ZnCO₃) from reactions using different ratios ofZn: [(HMTETA)(Fe(NO)₂)₂] complex were produced using the same experimentprocedure described above (Table 1). As the zinc metal ratio increased,the supplying ratio of carbon dioxide also increased. Reaction wasdeemed to be completed until the product in the reaction flask had allturned to white colored zinc carbonate. The white colored zinccarbonates were then identified by FTIR (IR: ν_(CO3) 1445 cm⁻¹ (KBr))and elemental analysis (Calc. C 9.58%, found C, 9.55%).

TABLE 1 Entry Metal Solvent Zn:[(HMTETA)(Fe(NO)₂)₂] ZnCO₃ (Yield) 3-1 ZnH₂O 10 mmol:0.1 mmol 89.7% 3-2 Zn H₂O 50 mmol:0.1 mmol 91.24% 3-3 Zn H₂O 0.1 mol:0.1 mmol 96.3% 3-4 Zn H₂O  0.5 mol:0.1 mmol 94.8%

Example 4

Complex [(HMTETA)(Fe(NO)₂)₂] (0.046 g, 0.1 mmol) and magnesium metal(0.243 g, 10 mmol) were loaded in the 500 mL flask and dissolved in H₂O(100 mL). CO₂ gas (490 mL, 20 mmol) was then injected into the H₂Osolution of complexes Mg-[(HMTETA)(Fe(NO)₂)₂] with a gastight syringe atambient temperature. After the heterogeneous mixture solution wasstirred at ambient temperature for 20 hours, the white solid magnesiumcarbonate (MgCO₃) precipitated from the H₂O solution accompanied byrelease of CO characterized by GC (gas chromatography) analysis of gassamples in the headspace. The white precipitate was collected throughfiltering and dried to yield pure MgCO₃ (yield 0.674 g, 80%). IR ν_(NO)stretching frequency 1486, 1424 cm⁻¹ (KBr) suggests the formation ofMgCO_(3.)

Example 5

Iron metal (0.559 g, 10 mmol) and complex [(HMTETA)(Fe(NO)₂)₂] (0.046 g,0 1 mmol) were loaded in the 500 mL flask and dissolved in H₂O (100 mL).CO₂ gas (490 mL, 20 mmol) was then injected into the H₂O solution ofcomplexes Fe-[(HMTETA)(Fe(NO)₂)₂] with a gastight syringe at ambienttemperature. After the heterogeneous mixture solution was stirred atambient temperature for 72 hours, the red-brown solid iron carbonate(FeCO₃) precipitated from the H₂O solution accompanied by release of COcharacterized by GC (gas chromatography) analysis of gas samples in theheadspace. The red-brown precipitate was collected through filtering anddried to yield pure FeCO₃ (yield 0.928 g, 80%). IR V_(NO) stretchingfrequency 1419 cm⁻¹ (KBr) suggests the formation of FeCO_(3.)

In the present invention, metal carbonates can be produced at roomtemperature and under the pressure of about 1 atm. by the method of thepresent invention without the need of additional electrical or photoenergies. Moreover, the reaction of the method of the present inventioncan be achieved in organic phase or aqueous solutions in the presence ofthe catalyst as described above. Hence, the method of the presentinvention is simple, energy-saving, and cheap compared to that of theconventional methods.

Although the present invention has been explained in relation to itspreferred embodiment, it is to be understood that many other possiblemodifications and variations can be made without departing from thespirit and scope of the present invention as hereinafter claimed.

What is claimed is:
 1. A method for producing metal carbonate,comprising following steps: (A) providing a first mixture of metal and asolution of a catalyst represented by the following formula (I):(Fe(NO)₂)₂L  (I) wherein L is a ligand represented by the followingformula (II);(R₁R₂)N—(CH₂)₂—N(R₃)—(CH₂)₂—N(R₄)—(CH₂)₂—N(R₅R₆)  (II) wherein each ofR₁, R₂, R₃, R₄, R₅, and R₆, independently is hydrogen, or C₁-C₃ alkyl;and (B) introducing carbon dioxide to the first mixture to form a secondmixture and obtaining a product.
 2. The method of claim 1, furthercomprising step (C) drying or filtering the second mixture to collectthe product of step (B).
 3. The method of claim 1, wherein the metal isNa, Mg, Zn, Fe, or the combination thereof.
 4. The method of claim 1,wherein the step (B) is performed at room temperature.
 5. The method ofclaim 1, wherein R₁ and R₂ are the same.
 6. The method of claim 1,wherein R₃ and R₄ are the same.
 7. The method of claim 1, wherein R₅ andR₆ are the same.
 8. The method of claim 1, wherein R₁, R₂, R₃, R₄, R₅,and R₆ are hydrogen, or methyl.
 9. The method of claim 1, wherein L is1,1,4,7,10,10-hexamethyltriethylenetetramine
 10. The method of claim 1,wherein L is triethylenetetramine
 11. The method of claim 1, wherein thesolution of a catalyst in step (A) is an aqueous solution, or organicsolution.
 12. A compound represented by the following formula (I):(Fe(NO)₂)₂L  (I) wherein L is a ligand represented by the followingformula (II);(R₁R₂)N—(CH₂)₂—N(R₃)—(CH₂)₂—N(R₄)—(CH₂)₂—N(R₅R₆)  (II) wherein each ofR₁, R₂, R₃, R₄, R₅, and R₆, independently is hydrogen, or C₁-C₃ alkyl.13. The compound of claim 12, wherein R₁ and R₂ are the same.
 14. Thecompound of claim 12, wherein R₅ and R₆ are the same.
 15. The compoundof claim 12, wherein R₃ and R₄ are the same.
 16. The compound of claim12, wherein R₁, R₂, R₃, R₄, R₅, and R₆ are hydrogen, or methyl.
 17. Thecompound of claim 12, wherein L is1,1,4,7,10,10-hexamethyltriethylenetetramine
 18. The compound of claim12, wherein L is triethylenetetramine.
 19. The compound of claim 12,which is used for catalyzing the reaction for producing metal carbonate.20. The compound of claim 19, wherein the metal is Na, Mg, Zn, Fe, orthe combination thereof.